A great number of window coverings now on the market are installed by users after purchase. As the specifications of the purchased window coverings often do not exactly match the width of doors or windows in the houses, users have to trim the width of the window covering assembly during installation to match the width of the doors or windows.
FIGS. 1 and 2 illustrate a conventional window covering 10 which has an upper rail 11 and a lower rail 12 and a retractable and extendable window covering assembly 13 located between the lower rail 12 and the upper rail 11. The window covering assembly 13 has an adhesive tape 130 on the bottom end with a release sheet 14 attached thereon. While the window covering assembly 13 may be cut and trimmed to match the width of a door or window, it also creates problems as follow:
1. The window covering assembly 13 usually has a portion on one side not bonding with the upper rail 11 and the lower rail 12. After the window covering assembly 13 is cut, the one side of the window covering assembly 13, the upper rail 11 and the lower rail 12 form a smaller included angle. Peeling off the release sheet 14 from the attached adhesive tape 130 on the bottom end of the window covering assembly 13 is difficult (referring to FIG. 2). As a result, bonding of the window covering assembly 13, the upper rail 11, and the lower rail 12 is not always in a desired condition.
2. The release sheet 14 attached to the adhesive tape 130 is formed at a length same as the unglued portion of the window covering assembly 13. After the window covering assembly 13 has been trimmed, peeling off the release sheet 14 can be done only in the smaller included angle between the window covering assembly 13, the upper rail 11, and the lower rail 12. Peeling operation of the release sheet 14 is difficult and takes more time. There are still rooms for improvement.